Centre beam freight cars are freight cars in which a beam structure is located centrally, and longitudinally, in the freight car above the load carrying platform. The end of the beam are anchored in the end bulkheads of the car. The beam serves as a sink for stresses transferred from a further beam structure which is located below the load carrying platform.
Centre beam freight cars are used primarily to transport large packages or bundles which do not require much protection from the elements. Therefore, a freight car should have wide utility but need not have much covering for freight to be transported. Also, the tare mass of the empty car should not constitute a high proportion of the mass of a fully laden car.
Early freight cars required considerable mass in the central beam structure located below the load carrying platform in order to accommodate safely lateral and compressive stresses. Taylor, in U.S. Pat. No. 3,244,120 describes a freight car in which this considerable mass is much reduced. This freight car is a flat car type of railroad car which has a longitudinally extending, composite beam comprising a load carrying composite stem and cross members forming the floor of the freight car. A beam extends upward from each end of the composite stem. A compression member connects the upper ends of the upwardly projecting beams. The compression member spans the freight car at the same height as the top of the freight car bulkheads. The composite stem, upwardly extending beams and compression member form what is now referred to as the centre beam. Further reduction of the tare mass in proportion to the laden car mass is not safe with this structure as such a freight car could not accommodate safely the lateral forces which may arise in normal use.
This problem was partially overcome by Wagner in U.S. Pat. No. 3,734,031 and in the corresponding Canadian Pat. No. 939,197. In these patents, a centre beam freight car is described which has a central supporting structure comprising a vertical plate having a top compression structure. The vertical plate has a number of beams extending vertically upward on either side of it to provide additional support. The top compression structure is, in essence, a horizontal metal plate joined centrally to the vertical plate and has horizontal stiffening members joined to both edges of the horizontal plate. The horizontal plate and stiffening members form a trough like structure which may be used to store "tie-down" equipment such as ropes and the like. However, the primary utility of the top structure is to provide resistance to lateral stresses which arise during use of the car; in other words, to prevent snaking.
However, the tare mass of Wagner's freight car still constitutes a high proportion of the mass of a fully laden car. Furthermore, snow and the like can collect in the trough-like structure and adjacent the vertical plate. This may cause difficulty in retrieving or attaching any "tie-down" equipment.
Accordingly, it is an object of this invention to provide a centre beam freight car which is adequately protected against lateral and compressive stresses which may arise in normal use and which has a tare mass which constitutes at least a lower proportion of the fully laden mass than prior art centre beam freight cars.